Re: [dpdk-dev] [PATCH] bus/pci: fix mmap PCI resource

[Thomas Monjalon <thomas@monjalon.net>]

10/07/2020 12:07, Thomas Monjalon:
> 10/07/2020 11:54, David Marchand:
> > On Wed, Jul 8, 2020 at 11:26 AM <alvinx.zhang@intel.com> wrote:
> > > From: Alvin Zhang <alvinx.zhang@intel.com>
> > >
> > > When mapping a PCI BAR containing an MSI-X table, some devices do not
> > > need to actually map this BAR or only need to map part of them, which
> > > may cause the mapping to fail. Now some checks are added and a non-NULL
> > > initial value is set to the variable to avoid this situation.
[...]
> > > --- a/drivers/bus/pci/linux/pci_vfio.c
> > > +++ b/drivers/bus/pci/linux/pci_vfio.c
> > > @@ -547,6 +547,14 @@
> > >                         bar_index,
> > >                         memreg[0].offset, memreg[0].size,
> > >                         memreg[1].offset, memreg[1].size);
> > > +
> > > +               if (memreg[0].size == 0 && memreg[1].size == 0) {
> > > +                       /* No need to map this BAR */
> > > +                       RTE_LOG(DEBUG, EAL, "Skipping BAR%d\n", bar_index);
> > > +                       bar->size = 0;
> > > +                       bar->addr = 0;
> > > +                       return 0;
> > > +               }
> > 
> > We already have a check on bar size == 0.
> > Why would we have this condition?
> > Broken hw?
> > 
> > 
> > >         } else {
> > >                 memreg[0].offset = bar->offset;
> > >                 memreg[0].size = bar->size;
> > > @@ -556,7 +564,9 @@
> > >         bar_addr = mmap(bar->addr, bar->size, 0, MAP_PRIVATE |
> > >                         MAP_ANONYMOUS | additional_flags, -1, 0);
> > >         if (bar_addr != MAP_FAILED) {
> > > -               void *map_addr = NULL;
> > > +               /* Set non NULL initial value for in case of no PCI mapping */
> > > +               void *map_addr = bar_addr;
> > > +
> > 
> > It took me some time to understand this code...
> > Anyway, we have a regression in the librte_pci.
> > This is where the fix should be.
> 
> Yes, I am going to send a fix.

Patch sent: https://patches.dpdk.org/patch/73741/

This patch is marked as rejected, but please follow-up on cleanup.

> > We can cleanup this code later.
> 
> Yes please, this function isn't understandable and lack of comments.
> Anatoly please?